试题与答案

如图所示三个物体质量分别为m1、m2、m3,带有滑轮的物体放在光滑水平面上,滑轮

题型:选择题

题目:

如图所示三个物体质量分别为m1、m2、m3,带有滑轮的物体放在光滑水平面上,滑轮和所有接触处的摩擦及绳的质量均不计,为使三个物体无相对运动,则水平推力F为(  )

A.

(m1+m2+m3)m2g
m1

B.

(m1+m2+m3)m2g
m2

C.

(m1+m2+m3)m1g
m2

D.

(m1+m2+m3)m2g
m3

答案:

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参考答案:D

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When you’re trying to find the best place to live,choosing a neighborhood is almost as important as choosing a house or an apartment.小题1:.

Crime and Safety

Research the Internet.Use a search engine to find some information about the crime(犯罪) reports in that neighborhood.

 小题2: The police department will provide details about a particular area. This is probably your best source of information on crime and safety.

Drive around the area.Look for crime signs such as broken windows. Do homes have high fences or bars on accessible windows?

Look and Feel

 小题3: Take a note of(留意)the condition of the houses,the front yards, the streets and side walks.See if people you meet make eye contact with you.小题4:  Note the traffic and speed and see if the streets seem quiet or noisy.

Transportation

How long wilt it take to get to work? Will you be going with or against traffic? Is there public transportation available? If you need access to the airport,how far is the drive?

Schools

The sign of a good neighborhood is a well-kept school.  小题5: Another thing to consider is how your child will get to school. Is there public transportation? Can they walk? Is it safe? How far is it to drive?

A.Contact the local police department.

B.Find out the value of the house in the neighborhood.

C.If they do, it’s probably a safe and friendly community.

D.Spend time walking through the neighborhood.E. If there are bars close by, how noisy will it be on weekends?

F. It needs to be safe, affordable and provide you with everything that you need.

G. And if you have children, this is probably the first consideration.

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